George D. Brunton

The crystal structure of Li4UF8

Abstract The compound Li 4 UF 8 crystallizes in space group Pnma with a 0 = 9·960, b 0 = 9·883 and c 0 = 5·986. The X-ray density is 4·71 g/cm 3 and Z = 4. Twenty-four positional parameters, four anisotropic uranium temperature factors, and seven isotropic temperature factors were determined from 634 independent reflections measured by the 2θ-scan technique with a scintillometer. The parameters were refined by least squares to an R factor of 0·082. Absorption corrections were made for Cu K α radiation on an oblate spheroid with a short 36 μ axis, [001], and a 64 μ dia. for the circular section. The U 4+ ion has 8F − nearest neighbors with bond distances of 2·21–2·39 A. The next three nearest neighbors are 2Li + and another F − at 3·27 and 3·30 A respectively. The nine F − ions are at the corners of a 14-faced polyhedron which has the form of a triangular prism with pyramids on each of the three prism faces and the two Li + ions are at the centers of irregular F − octahedra which share faces with the uranium polyhedron. The Li + F − distances are 1·82–2·28 A.

Condensed equilibria in the uranium(III)-uranium(IV) fluoride system

Abstract The phase diagram of the condensed system UF 3 -UF 4 was established experimentally. The system is characterized by the occurrence of a single eutectic invariant point, at 32 mole% UF 3 , m.p. 865°C; by the absence of intermediate compounds; and by the behavior of UF 3 acting as crystalline solvent for U 4+ . Solid state equilibria were found to differ substantially from those reported previously by British and Russian workers. Uranium(IV) was found to undergo substitutional solid solution in UF 3 , reaching a maximum solubility at the solidus at UF 3 -UF 4 (67-33 mole%). As was to be expected analogous solution behavior with UF 4 acting as a solute for U 3+ , does not occur.

The crystal structure of Na3CrF6

The structure of Na3CrF6 is isomorphous with that of Na3FeF6 and Na3AlF6 (cryolite). It crystallizes in space group P21c with ao = 9.6618±0.0009, bo = 5.7021±0.0003, co = 5.4913±0.0003A and β = 125.021±0.005 degrees.

The crystal structure of Li2MoF6

Abstract Crystals of Li 2 MoF 6 are tetragonal P4 2 2 1 2 with a o = 4.6863(7) and c o = 9.191(2)A, Z = 2 and the calculated density is 3.687 g/cc. The Li + and Mo 4+ ions are octahedrally coordinated. The Li-F distances range from 2.017(2) to 2.102(7)A and the Mo-F distances range from 1.927(2) to 1.945(2)A. The MoF 6 -- ion is coordinated by 10 Li + .

Phase relations in the system KFCeF3

Abstract The system KFCeF 3 was investigated as a function of temperature and composition by thermal analysis, differential thermal analysis, and gradient quenching. Crystalline phases in the quenched samples were identified principally by use of the polarizing microscope, but selected samples were examined by X-ray powder diffraction. Three compounds were identified: 3KF·CeF 3 , KF·CeF 3 , and KF·2CeF 3 which melt incongruently at 675±10°C, 755±5°C, and 1135±15°C, respectively. Of these only KF·CeF 3 is stable below 585°C. Three peritectic equilibria were observed corresponding to these incongruent melting points at 24, 32, and 63 mole % CeF 3 . The αKF·2CeF 3 phase exhibits a substantial solid solubility for KF at temperatures above 795°C which results in a region of cubic solid solution whose properties vary over the composition range from 50 to 66- 2 3 mole % CeF 3 .

The absolute configuration of RbClO3

The positional parameters of the structure of RbClO3 have been determined from 171 x-ray reflections; ano = 6.092(1)Aco = 8.173(2)A, ϱcal = 3.203 g/cc3and S.G. = R3m. The absolute configuration of the structure was determined by a least-squares adjustment of the complex anomalous dispersion of Rb and Cl. The ClO distances are 1.478(5)A and the RbO distances are 3.530(8)A.

The crystal structure of Na2LiBe2F7

Abstract Na 2 LiBe 2 F 7 is isostructural with the mineral s melilite and hardystonite. The compound crystallizes with space group P42 1 m, a o = 7.593(2) A , c o = 4.841(2) A and Z = 2. The Be 2 F 7 −3 ion is composed of two Be-F tetrahedra that share a corner and have co-planar bases. The four Be-F distances range from 1.505(5) to 1.591(5)A and the tetrahedral angles range from 104.4(3) to 114.8(3)°. The Li + ion is tetrahedrally coordinated with all four Li-F distances equal to 1.826(6)A. There are eight NaF distances ranging from 2.378(3) to 2.657(3)A.